1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, and more particularly, to a fabrication method of a color filter of an LCD device which can simplify processes and reduce the cost of fabrication by not using a photo mask.
2. Description of the Related Art
Recently, various portable electric devices such as mobile phones, personal digital assistants (PDA), and notebook computers have been developed, and therefore, the needs for a flat panel display device used in small, light weight, and power-efficient devices for such portable devices have correspondingly increased. To meet such needs, flat panel display device technologies such as liquid crystal display (LCD) technology, plasma display panel (PDP) technology, field emission display (FED) technology, and vacuum fluorescent display (VFD) technology have been actively researched. Of these flat panel display devices, the LCD is most prevalent due to available mass production techniques, efficient driving schemes, and superior image quality.
FIG. 1 is a schematic view showing a sectional surface of a general LCD device. As shown in FIG. 1, the LCD 1 comprises a lower substrate 5, an upper substrate 3, and a liquid crystal layer 7 formed between the lower substrate 5 and the upper substrate 3. The lower substrate 5 is a driving device array substrate. A plurality of pixels (not shown) are formed on the lower substrate 5, and a driving device such as a thin film transistor (TFT) 9 is formed on each pixel. The upper substrate 3 is a color filter substrate, and a color filter layer for reproducing real color is formed thereon. Further, a pixel electrode 6 and a common electrode are formed on the lower substrate 5 and the upper substrate 3, respectively. An alignment layer is formed on the lower substrate 5 and the upper substrate 3 to align liquid crystal molecules of the liquid crystal layer 7 uniformly.
The lower substrate 5 and the upper substrate 3 are attached by a sealing material (not shown), and the liquid crystal layer 7 is formed therebetween. In addition, the liquid crystal molecules are reoriented by the driving device formed on the lower substrate 5 to control the amount of light transmitted through the liquid crystal layer, thereby displaying information.
Fabrication processes for a LCD device can be divided into a driving device array substrate process for forming the driving device on the lower substrate 5, and a color filter substrate process for forming the color filter on the upper substrate 3.
At first, a plurality of gate lines and data lines are arranged on the lower substrate to define a pixel area by the driving device array process and the thin film transistor connected to the both gate line and the data line is formed on the each pixel area. Also, a pixel electrode, which is connected to the thin film transistor to drive the liquid crystal layer according to a signal applied through the thin film transistor, is formed by the driving device array process.
Also, the color filter process forms the black matrix 8 on the upper substrate 3, forms the color filter 2 on upper part of the black matrix 8, and forms the common electrode 4 on the color filter.
There are methods for fabricating the color filter such as a pigment dispersing method and an electrophoresis deposition method. In particular, the pigment disperse method forms the color filter by coating, exposing, developing and burning pigment composition dispersed on a photoresist. The fabrication method of color filter using the pigment disperse method will be described with reference to FIG. 2.
First, as shown in FIG. 2A, a transparent substrate 21 is provided, material for forming the black matrix such as chrome and organic material is coated on the substrate 21, and after that, a black matrix pattern 22 is formed using a photolithographic process. Next, as shown in FIG. 2B, material for forming red color filter film 23 is coated thereon, and a predetermined area is exposed using a photo mask 28 and developed to form the red color filter film 23a as shown in FIG. 2C. After that, the above process is repeated using materials for green and blue color filters instead of using the red color filter film material, and, the green and blue color filter films 23b and 23c are respective formed as shown in FIG. 2d. The R, G and B color filter film 23 is thus completed.
However, in the fabrication method of the color filter according to the related art, an expensive photo mask is used, and photolithographic processes such as the color filter coating, exposure and development are repeatedly performed. Therefore, the fabrication cost is increased.